Download DNA RNA

Protein Synthesis (to make
proteins)
What is Protein Synthesis?
Flow of Genetic Information:
DNA
RNA
Protein
DNA holds the code for protein
synthesis but cannot leave the
nucleus
Protein Synthesis is performed at the
ribosomes in the cytoplasm
The cell uses RNA to copy the code
from DNA and bring it to the
ribosomes
RNA – Ribonucelic Acid
I.
Nitrogenous Bases
a. Adenine
b. Cytosine
c. Guanine
d. Uracil
I.
Simple Sugar – a ribose rather than a
deoxyribose
Phosphate Groups
II.
II. Structure
a. A nucleic acid
backbone
b. single strand of
nucleotides
c. Sugar is ribose
d. Contains uracil base
instead of thymine
Difference between DNA and RNA
 DNA
 Double
strand
 Deoxyribose
 Thymine
RNA
single strand
ribose
uracil
III. Types of RNA
Three types of RNA are
used to make
proteins
a. mRNA – messenger
RNA
b. rRNA – ribosomal RNA
c. tRNA – transfer RNA
IV. mRNA Function
A. transcribe DNA code
B. take code outside of nucleus to ribosome
C. give instructions to ribosome on how to
build protein
How does DNA transfer info to
RNA?
A=U
G=C
T=A
No T’s in RNA
V. tRNA Function

To deliver amino
acids to the
ribosome as it is
building
(synthesizing)
protein
VI. rRNA Function
 where
translation of RNA to protein
takes place
 Ribosomes
are made up of protein
and ribosomal RNA (rRNA)
Remember:
How many different amino acids are
there?
20
Look at your notes - What makes each
amino acid different from one another?
R groups
VIII. The CODE!!
A. James Watson and Francis Crick, with
the help of Rosalind Franklin’s X-ray
crystallography images unraveled the
structure of DNA:
B. The fact that bases paired led directly
to a theory of how DNA codes for
proteins. It took a few years to
determine that the bases spell threeletter “words” called codons
mRNA Codons

3 letters on mRNA are called codons.
These three letter codes are used to
determine which Amino Acid is to be
placed on the protein.
Ex: TAC
AUG = Start Codon (Methionine)
This is where you begin translation of DNA’s
code given to mRNA
See the mRNA codon chart (slime
green)

Write the codon for Proline here:

Glycine?

Which amino acid has the most codons?

Which amino acid has the fewest?

Start codon starts each protein

Three codons tell a ribosome to stop
making a protein. List them here:
Transcription?
- Copying the portion of DNA that carries the
code for a protein.
http://www.youtube.com/watch?v=ztPkv7wc3
yU&feature=related
mRNA Synthesis (Transcription begins with a
promoter on DNA, site RNA polymerase
binds to on DNA to begin transcription).
- A mRNA is transcribed (built) using
unwound DNA’s code as a template.
- RNA nucleotides find their compliment.
- RNA Polymerase is the enzyme that brings
in the nucleotides
- Completed when reaches terminator
sequence on DNA – ending transcription
The original strand is used as the
template.
Result:
The resulting mRNA looks exactly like the
template strand of DNA, with one
important distinction
each T is replace with a U.
http://www.youtube.com/watch?v=Jqx4Y0OjWW4&fea
ture=related
Where does it go?
The RNA releases from DNA and is then
edited before leaving the nucleus
Practice Transcription
DNA
Strand
3 ‘ T A C G A T G C A T C G 5’
RNA
Strand
5 ‘ A U G C U A C G U A G C 3’
http://www.youtube.com/watch?v=NjczQKjFcks&feature=related
Translation
-
The process of interpreting mRNA to build
a chain of amino acids that make up a
protein.
http://www.youtube.com/watch?v=B6O6uRb1
D38&feature=related
How does it work?
i. mRNA leaves the nucleus and heads
to the cytoplasm where the
ribosomes are located.
Remember: Ribosomes are where
translation will occur
• Each sequence of nucleotides is a
codon (mRNA codon). Each codon
codes for a specific amino acid
ii. Amino acids are brought to the
ribosome by tRNA.
• There are 20 different tRNA molecules,
one for each type of amino acid.
• tRNA anticodon finds their complimentary
codon on mRNA.
Anticodon – 3 letters found to match the mRNA’s
codon.
– mRNA codon:
UAA CGA GGC
– tRNA anticodon: AUU GCU CCG
iii. Peptide bonds form between the
amino acids forming a polypeptide.
iV. Translation stops when a stop
codon is reached.
Video:
http://www.youtube.com/watch?v=41_
Ne5mS2ls&feature=related
Video:
http://www.youtube.com/watch?v=983l
hh20rGY&feature=related